This project re-examines the perceptual weight of vowel duration and the first two vowel formant frequencies as determinants of phonologically short and long vowels in Swedish. Based on listeners' responses to synthesized sets of materials for [I]-[i:] [ ]-[o:] and [a]- [a:], results indicate that vowel duration is of primary importance for distinguishing [I) from [i:] and [ ] from [o:], whereas both formant frequencies and vowel duration were found to influence the perception of [a] from [a:].